1. Field of the Invention
The present invention relates to disk drive for computer systems. More particularly, the present invention relates to a disk drive that caches initial host requested data in non-volatile semiconductor memory to reduce start-up time of a host computer.
2. Description of the Prior Art
Computer systems such as personal computers (PCs) execute an operating system that is typically stored on a disk of a disk drive. When powered on during an operating system (OS) boot, the host computer reads the OS boot data from the disk drive as part of a “start-up” process. In mobile computing applications, such as with laptop computers, the host computer may enter a “hibernation” mode to conserve power by powering down the disk drive and other components. Before entering the hibernation mode an “image” of the host computer's memory representing an operating state (e.g., OS boot data, application data, video graphics data) is 18 stored as a file on the disk drive. When the host computer “wakes” from the hibernation mode the operating state is restored during the start-up process by reading the image file from the disk. Desktop computers may also implement a hibernation mode as disclosed in U.S. Pat. No. 6,209,088 which is incorporated herein by reference.
When the disk drive is powered on (in connection with booting or waking the host computer) the disk drive must perform a mechanical initialization process wherein the disk is spun up to an operating speed and the mechanics calibrated (e.g., calibrating the servo system) before the data stored on the disk can be accessed, creating an undesirable delay during the start-up process. This delay is apparent to the end user in various applications, such as desktop computing, enterprise computing, mobile computing, and game computing. The start-up process also consumes power in mobile applications due to the mechanical components consuming power, such as a voice coil motor actuating a head while reading the initial host requested data from the disk.
There is, therefore, a need to reduce the start-up time of a host computer as well as reduce power consumption in mobile devices employing a hard drive.